Activity Title: Make Your Own Stethoscope
- School Age
What Do I Need?
- Duct tape or other strong tape
- Plastic funnel
- A cardboard tube from a paper-towel roll
- Stopwatch or clock that counts seconds
- A volunteer who can safely exercise intensely for one minute
How Do I Do It?
- Put the narrow end of the funnel into the cardboard tube.
- Using a strip of duct tape or other strong tape, tape the funnel and cardboard tube together. Make sure there are no gaps or spaces where you tape them together.
- Your stethoscope is now ready to use! Practice listening to the heartbeat of a volunteer by putting the funnel on the left side of the volunteer's chest. Make sure the funnel is flat against their chest. Put your ear against the hole at the end of the cardboard tube. Do you hear the heartbeat?
Tip: If it is noisy or the volunteer is wearing thick clothing, it may be hard to hear the heartbeat, so you may need to adjust conditions accordingly.
- After the volunteer has been resting in a chair for a few minutes, listen to the heartbeat and count how many times it beats in 10 seconds. Multiply this number by six. This is the resting heart rate of the volunteer in beats per minute (bpm).
- Ask the volunteer to exercise in place for one minute by doing jumping jacks or running in place. Right after the volunteer has stopped exercising, listen to the heartbeat and count how many times it beats in 10 seconds. Multiply this number by six. This is the active heart rate of the volunteer in beats per minute (bpm).
What's the Science Behind It?
When people exercise, their bodies need more oxygen, and consequently their hearts beat faster and their heart rates increase. This is why you most likely found that when your volunteer exercised, the heart rate increased compared to the resting heart rate. In addition, genetics, gender, age, and health all affect people's heart rates. The heart rates in people who exercise regularly usually will not increase as much during exercise. Regular exercise strengthens the heart so that it does not need to work as hard to do the same amount of exercise.
While you can determine someone's resting heart rate by counting the number of beats in 15 seconds and multiplying by four to get the beats per minute (bpm), to calculate a heart rate immediately after exercise it is better to count the number of beats for 10 seconds and multiply that value by six (to get the bpm). Because the heart will quickly slow down after exercise, the heart rate should be measured immediately after a person has stopped exercising (or while they exercise, if possible).